text: /*
   * Copyright (c) Facebook, Inc. and its affiliates.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #include <folly/experimental/coro/Materialize.h>
  
  #if FOLLY_HAS_COROUTINES
  
  namespace folly {
  namespace coro {
  
  template <typename Reference, typename Value>
  AsyncGenerator<Reference, Value> dematerialize(
      AsyncGenerator<CallbackRecord<Reference>, CallbackRecord<Value>> source) {
    while (auto item = co_await source.next()) {
      if (item->hasValue()) {
        // Value
        co_yield std::move(*item).value();
      } else if (item->hasNone()) {
        // None
        co_return;
      } else if (item->hasError()) {
        // Exception
        std::move(*item).error().throw_exception();
      } else {
        DCHECK(false);
        std::terminate();
      }
    }
  }
  
  } // namespace coro
  } // namespace folly
  
  #endif // FOLLY_HAS_COROUTINES
  